Tunnel blasting in Italy – challenging conditions
One of the larger road construction projects in Europe today is a new motorway system in the Italian regions of Marche and Umbria. The four year project includes 160 km of roadway with 30 km inside tunnels. It´s a challenging engineering project located largely in the geologically complex Appenine hills with low overburdens at the tunnelling sites. Densely populated villages and other structures on the surface include fragile historical sites with medieval churches and other sensitive buildings. This means that monitoring of vibration and noise levels is an essential part of the blasting process.
Several large construction companies involved have entrusted the explosives engineering, consulting and vibration monitoring to Udine-based geophysics and blasting experts, Seismoter Europe. Chief consultant engineer in charge of monitoring, Demosthenes A. Efstratiadis, explains the requirements:
– Peak particle velocity of ground vibration has to be measured during every single blast, both open-air and underground. The UNI9916 national standard (with the same limit values as German standard DIN4150-3) must be adhered to. The imposed limit value of particle velocity for historical buildings is 3 mm/s (for the entire frequency spectrum). The limit value for dwellings is 5 mm/s (from 1 to 5 Hz) and 15 mm/s (from 10 to 50 Hz). Every single blast has to be calibrated on the basis of the measured data/results of the previous blast.
Successful change of measurement system
– Vibrations monitoring began at the end of March 2011 and will continue for the duration of blasting operations. Some particular measurement challenges concerned public relations issues, which included
informing the local population regarding the effectiveness of the vibration monitoring system. These and other aspects of my work have been considerably facilitated by our use of the Sigicom INFRA measurement
system, says Dr. Efstratiadis.
Other monitoring instruments were used by the previous consultant engineer. The INFRA system made a difference that was noticed by the customer, the supervisors and the local communities. The better reliability and the more permanent aspect of the Sigicom INFRA monitoring station instead of the temporary arrangement of the previous instruments was appreciated, especially by the home owners. The customer’s benefit was the fact that every single blast can be examined in real time by all interested parties with no doubts regarding the authenticity of the measured data.
Immediate response and automatic reporting
At every blasting site Seismoter Europe uses an INFRA data logger with two geophones, one sound level sensor and one air humidity/temperature sensor connected to the same bus cable. The system works on a 24 hour basis. The reporting system is Sigicom’s INFRA Net, which provides fresh blast data and a detailed daily report on measurement data. This information is also available on-line at a web portal to all parties with an access code in their computers, and a more general monthly report as well.
The INFRA Measurement system has fulfilled all requirements and exceeded my expectations. My satisfaction with the system is 10 on a scale from 1 to 10. Working under difficult circumstances in this project I have found a valuable ‘ally’ in the INFRA system. I particularly appreciate the reliability and the immediate response of the system and I strongly recommend it to my colleagues in the blasting field. Our customers are fully satisfied as well, and most of all feel safe and comfortable with our monitoring of the ground vibration problem, Dr Efstratiadis concludes.